leetcode376. 摆动序列

class Solution {

    
    public int wiggleMaxLength(int[] nums) {
        if (nums.length == 1) return 1;

        int curDiff = 0;
        int preDiff = 0;
        int ans = 1;//把初始结点算上

        for (int i  = 0; i < nums.length-1; i++) {
            curDiff = nums[i+1] - nums[i];

            if (curDiff > 0 && preDiff <= 0 ||( preDiff >= 0 && curDiff < 0)) {//这里的preDiff=0
                ans++;                                          //的时候只是在第一次用到                        
                preDiff = curDiff;
            } 
        }

        return ans;
    }
}